Problem: Nadia just found beautiful yarn for 20 percent off at her favorite yarn store. She can make 1 scarf from $\frac{2}{5}$ of a ball of yarn. If Nadia buys 12 balls of yarn, how many scarves can she make?
Solution: We can divide the balls of yarn (12) by the yarn needed per scarf ( $\frac{2}{5}$ of a ball) to find out how many scarves Nadia can make. $ \dfrac{{12 \text{ balls of yarn}}} {{\dfrac{2}{5} \text{ ball per scarf}}} = {\text{ number of scarves}} $ Dividing by a fraction is the same as multiplying by the reciprocal. The reciprocal of ${\dfrac{2}{5} \text{ ball per scarf}}$ is ${\dfrac{5}{2} \text{ scarves per ball}}$ $ {12\text{ balls of yarn}} \times {\dfrac{5}{2} \text{ scarves per ball}} = {\text{ number of scarves}} $ ${\dfrac{60}{2}\text{ scarves}} = 30\text{ scarves}$ Nadia can make 30 scarves.